Resonator silencer



y 9, E. E. WILSON 2,

RESONATOR SILENCER Original Filed Dec. 12, 1936,

Zinoentor Patented July 9, 1 946 General Motors Corporation, Detroit, Mich., a

' corporation of Delaware Original application December 12,1936, Serial No. 2 a

115,470. Divided and this application August 30, 1940, Serial No. 354,877

2 Claims. (01. 181-48) To attenuate the objectionable sound waves -which occur in the intake and exhaust systems of internal combustion engines, resonator silencers,

such as those disclosed in my prior applications Serial Nos. 470,700and 633,265 which were filed on July 25,1930, and September 15, 1932, respectively, are now commonly used. However, because the natural' frequencies of the resonators incorporated in these silencers are fixed and objectionable sound waves of difierent frequencies may occur in the intake or exhaust system of an internal combustion engine when it is operating at'difierent speeds but not simultaneously, itis frequently necessary, in order to attenuate all of the objectionable sound waves which occur in the intake or exhaust system of an internal combustion engine, to provide in it one or more resonators which are operative only when the engine is operating at some speed or speeds and anotheror other resonators which are operative only when the engine is operating at another speed or other speeds.

: The principal object of this invention is to provide resonator silencers in'which it is not necessary, in order to attenuate all of the objectionable sound waves which occur in the intake or exhaust system of the engine to which the silencer is to be applied, to provide in the silencer any resonators which are not operative simultaneous- "ly and thus to-minimize the number of resonators in the silencer.

V This object may be attained by providing in "the silencer a resonator whose natural frequency "may be varied. To render the natural frequency of' the resonator variable, the acoustical conductivity of its neck or necks or any of them and/or the voliune of its chamber or chambers or any of them may be made adjustable. This application, however, is concerned only with certain expedients disclosed but not claimed in my application Serial No. 115,470, filed December 12, 1936, which has matured into Patent No. 2,214,894, dated September 1'7, 1940, of which this application is a division, by which the natural frequency of the resonator may be rendered variable.

-' For a better understanding of the objects and nature of this invention, reference is made to the following specification in which there are described the embodiment of my invention which are illustrated in the accompanying drawing.

ln the accompanying drawing: Figures 1 to 5 are longitudinal sections through resonator silencers in accordance with this invention.

"duct is coaxial with the shell 10 and consists of tWo tubes of which one extends into and is sufficiently smaller-than the other that the overlapping portions of the tubes are separated by an annular aperture. One of the tubes is secured in each of the heads II and 12. The shell 10, its heads H and I2 and the tubes define a compartment which communicates with the duct defined by the tubes through the aperture between the overlapping portions of the tubes.

Within the compartment defined by the shell 10, its heads 1| and 12 and the tubes and 8| which define the duct of the silencer shown in Figure 1, there is disposed a false head 82 which encircles the tube BI and may be shifted lengthwise of the silencer. On the inner and outer edges of the false head 82, there are formed annular flanges 83 and 84 which fit snugly around the tube 8| and Within the shell 10, respectively. To shift the false head 82, there is provided a rod 85 which extends through a guide in the head 12 and Whose inner end is secured to the false head.

The compartment defined by the shell 19, its head ii, the false head 82 and the tubes 86 and 8| constitutes the chamber and the annular aperture 86 between the tubes 89 and 8| the neck of a simple resonator. The acoustical conductivity of the neck is, of course, fixed but the volume of the chamber and, thus, the natural frequency of the resonator, may be varied by shifting the false head 82.

The compartment defined by the shell 10, its heads 'II and 12 and the tubes 90 and 9| which define the duct of the silencer shown in Figure 2 is divided lengthwise into two chambers 92 and 93 by an annular partition 94 which encircles the tube 9| and is secured to itand the shell. Through the partition 94, there extends a tube which consists of two partly telescoped tubular elements 95 and 96 and interconnects the chambers 92 and 93. The tubular element 95 is secured in the partition 94 and the tubular element 95 may be shifted lengthwise of the tubular element 95 to Vary the effective length of the tube 9596. To shift the tubular element 96, there is provided a rod 91 which extends through a guide in the head 12 and whose inner end is secured to the tubular element 96.

The chambers 92 and93 constitute the chambers and the tube 95-46 and the annular apera compound resonator.

ture 98 between the tubes 90 and 9| the necks of a compound resonator. The volumes of the chambers and the acoustical conductivity of the neck 98 are, of course, fixed but the acoustical conductivity of the neck 95-96 and, thus, the natural frequencies of the resonator, may be varied by shifting the tubular element 96.

Within the compartment defined by the shell 10, its heads H and 12 and the tubes I and IOI which define the duct of the silencer shown in Figure 3, there is disposed a partition I02 which encircles the tube IOI and may be shifted lengthwise of the silencer. outer edges of the partition I02, there are formed annular flanges I03 and I04 which fit snugly around the tube IOI and within the shell 10, respectively. The partition I02 divides the compartment defined by the shell 10, its heads and the tubes I00 and NH into two chambers I05 and I06 which are interconnected by a tube I01 which extends through the partition. To shift the partition I02, there is provided a rod I08 which extends through a guide in the head 12 and whose inner end is secured to the partition.

The chambers I05 and I06 constitute the chambers and the tube I01 and the annular aperture I09 between the tubes I00 and IOI the neck of The acoustical conductivities of the necks are, of course, fixed but the volumes of the chambers and, thus, the natural frequencies of the resonator, may be varied by shifting the partition I02.

The compartment defined by the shell 10, its heads TI and 12 and the tubes I2I and I22 which define the duct of the silencer shown in Figure 4 is divided lengthwise into two chambers I23 and I24 by an annular partition I25 which encircles the smaller of the tubes and is secured to it and the shell. In the partition I25, there is secured a tube I26 which interconnuects the chambers I23 and I24. Through the head 12, there extends into the chamber I24 a tube I21 which terminates near the lower side of the shell and through which a liquid may be introduced into or withdrawn from the chamber I24.

The chambers I23 and I24 constitute the chambers and the tube I25 and the annularaperture I28 between the tubes I2I and I22 the necks of a compound resonator. The acoustical conductivities of the necks and the volume of the chamber I23 are, of course, fixed but th effective volume of the chamber I24 and, thus, the natural frequencies of the resonator, may be varied by introducing liquid into or withdrawing liquid from the chamber I 24 through the tube I21.

The larger of the tubes which define the duct of the silencer shown in Figure 5 consists of two partly telescoped tubular elements I30 and I3I of which the former is secured in the head TI and extends well beyond the inner end of and encircles the smaller of the tubes (I32) Within the compartment defined by the shell 10, its heads II and 12 and the tubes I30I3I and I32, there is disposed a false head I33 which encircles the tubular element I30 and may be shifted lengthwise of the silencer. To shift the false head I33, there is provided a rod I34 which extends through the head H and whose inner end is secured to the false head. On the inner and outer edges of the false head, there are formed annular flanges I35 and I36 which fit snugly around the tubular element I 30 and within the shell 10, respectively. The compartment defined by the shell 10, its head 12, the false head I33 On the inner and and the tubes II3I and I32 is divided lengthwise into three chambers I31, I38 and I39 by annular partitions I40 and I M which encircle the tubular element I30 and are secured to it and the shell. The partition I40 is imperforate but there is secured in the partition I4I a tube I 42 which connects the chamber I38 with the chamber I39 which communicates with the annular aperture I 43 between the tubes I30I3I and I32 through orifices I 44 in the tubular element I30 which may be partially or wholly covered by the flange I on the false head I33. The tubular element I3I of the tube I30-I3I, whose outer end is of smaller diameter than its inner end but of considerably larger diameter than the tube I 32, extends beyond the tubular element I 30 and may be shifted lengthwise of the silencer to vary the overlap between the tubes I30I3I and I32. To shift the tubular element I3I, there is provided a rod I45 which extends through guides in the head H, the false head I33 and the partitions I and MI and whose inner end is secured to the tubular element I3I.

The chambers I38, I39 and I3! constitute the chambers and the tube I 42, the orifices I44 and the annular aperture I43 the necks of a compound and simple resonator. The volumes of the chambers I38 and I 31 and the acoustical conductivity of the neck I42 are, of course, fixed but the volume of the chamber I39 and/or the acoustical conductivities of the necks I44 and I 43 and, thus, one or more of the natural frequencies of the resonator, may be varied by shifting the false head I33 and/or the tubular element I3I.

The silencers shown in Figures 1 to 5 were designed for installation on an internal combustion engine with the outer ends of the larger of the tubes (80, 90, I00, I2I and I30--I3I) which define their ducts connected to the air intake tube of the carburetor so that the air which enters the carburetor and cylinders of the engine flows through their ducts in the directions indicated by the arrows in the drawing. But any of the units shown in Figures 1 to .5 may be incorporated in an internal combustion engine exhaust silencer in which event its duct will, of course, be so disposed so that the exhaust gases of the engine will pass through it in the same direction as air passes through it when it is employed as an intake silencer.

In whichever manner the units shown in Figures 1 to 5 are to be installed the resonators will, of course, be so proportioned and dimensioned that when their adjustable elements are in one position they will respond to and attenuate by resonance objectionable sound waves of one or more frequencies which occur in the intake Or exhaust system of the engine on which the units are to be installed while the engine is operating at some speed or speeds and when their adjustable elements are in another position or other positions they will respond to and attenuate by resonance objectionable sound waves of another frequency or other frequencies which occur in the intake or exhaust system of the engine while it is operating at another speed or other speeds.

To vary the natural frequencies of the units shown in Figures 1 to 3 and 5 the rods (85, 91, I08, I34 and I) may be actuated manually and/0r automatically to shift the adjustable elements of the units in accordance with the shown in Figure 5 may be actuated synchronously or nonsynchronously by the same or different instrumentalities. The liquid employed to vary the efiective volume of the chamber I24 of the unit shown in Figure 4 may be obtained from the cooling system or the lubricating system of the engine on which the unit is installed or from a supply provided especially for the purpose. Any suitable means actuated manually and/r automatically may be provided to introduce and withdraw and control the introduction and withdrawal of the liquid from the chamber I24 i accordance with the requirements.

Examples of the instrumentalities that may be employed to vary the natural frequencies of the units shown in Figures 1 to 5 are disclosed in my Patent No. 2,214,894 previously referred to.

It will, of course, be understood that although I have described and illustrated my invention applied to the intake and exhaust system of internal combustion engines, it is also applicable to other devices in which objectionable sound waves of different frequencies occur under different conditions.

I claim:

1. In a silencer, a duct which includes a smaller tube and a larger tube which encircles and is radially spaced from a portion of the smaller tube, a shell which encircles and. is radially spaced from a portion of the duct, and walls which extend from the tubes to the shell and with the duct and the shell define a compartment which encircles the duct and communicates with it as a side branch through the aperture between the telescoped portions of the tubes, the wall which extends from the larger tube to the shell being adjustable lengthWise of the duct.

2. In a silencer, a shell, and a duct which extends through the shell and with it defines a compartment which encircles the duct, the duct including a larger tube and a smaller tube which extends into and is radially spaced from the larger tube to define with item aperture through which the compartment communicates with the duct, the larger tube being of smaller diameter at the end into which the smaller tube extends than at a distance from the mentioned end.

ERNEST E. WILSON. 

